Many bending processes are known, such as gravity bending, suction bending, press bending and bending between roller conveyors. Bending tools are always in contact to a greater or lesser extent with the glass to be bent, which generally leads to heat exchange. This is because the bending tool never has exactly the same temperature as the glass. Depending on the circumstances, this heat exchange may cause at least one of the following problems:                the glass may be cooled by the bending tool in locations where a deep bend is required, thereby causing local optical distortions and even breakages;        the temperature of the bending tool may vary with time (under the effect of repeated contact with glass panes that are at a different temperature), thereby making adjustment difficult and resulting in nonuniform batches; and        heat exchange must be compensated for by supplying additional heat, which costs money (additional hardware is required and energy consumption is increased).        
These problems may occur in bending processes in which the tools are contained in furnaces, or in bending processes in which the tools are not contained in furnaces.
The invention solves the aforementioned problems. The inventors now had the idea of manufacturing and using, for the bending, a tool with a very low density, so as to reduce its heat capacity and its thermal conductivity and make it more thermally neutral with respect to the glass to be bent. This low density is achieved by way of cells. The term “cell” is understood to mean a cavity in a solid material and this term is equivalent to pocket, orifice, void or free space. The cell is evacuated, or filled with a gas at atmospheric pressure or at a pressure lower or higher than atmospheric pressure. This gas is generally air. The cells open onto the molding area of the mold, proportionally reducing the area of real contact. Heat exchange between the mold and the glass is thereby greatly reduced.
US 2007/157671 teaches a bending process that uses a full mold, the interior of the full mold possibly being compartmentalized in order to apply suction or blowing through its molding area. By way of other documents describing bending using full molds, mention may be made of US 2007/144211, U.S. Pat. No. 5,769,919, U.S. Pat. No. 5,669,952 and U.S. Pat. No. 3,778,244.